1. Field of the Invention
The present invention relates to an apparatus and method for adjusting luminance, and more particularly, to an apparatus and method for automatically adjusting the luminance per region in a plurality of luminance regions of an image to be displayed, according to its average luminance value.
2. Description of the Related Art
As shown in FIG. 1, a general digital display apparatus displays weighted and time-shared image signals corresponding to bits of an image in chronological order, and represents a luminance difference between images, using integral values of these image signals. In other words, a dark image is displayed using only a low-weighted D0-D2 bit, and a light image is displayed by appropriately using a D0-D7 bit.
The general digital display apparatus is disadvantageous, however, in that an image may be displayed to be darker than expected in a case where the response speed of the general digital display apparatus does not come up to a predetermined level. This is because the display period of the image terminates before the luminance of the input image signal sufficiently increases with regard to a bit value, and thus, the image cannot be appropriately displayed.
Also, in general, an analog display apparatus, which uses conventional liquid crystal devices, has non-linear electro-optical characteristics as shown in FIG. 2. This non-linearity can be compensated for to a certain degree, using a gamma correction technique. However, a difference of contrast for a very dark portion or very light portion of an image is small with regard to a variation of applied voltage, and compensation cannot be sufficiently performed for a very dark or light portion. Therefore, the luminance of the image is displayed too darkly in the dark portion, whereas it is displayed too lightly in the light portion.